1. Field of the Invention
The present invention relates to an inkjet recording apparatus, particularly to an inkjet recording apparatus wherein a fabric of low rigidity that creases easily is used as a main recording medium, the inkjet recording apparatus comprising a conveyance belt.
2. Description of Related Art
In recent years, a wave of digitization is sweeping the field of images. Especially the textile printing industry is paying attention to the inkjet recording apparatus, rather than the prior art screen textile printing, because the inkjet recording apparatus meets requirements for quick response, small lots and a low volume production of a wide variety of products. Similarly, the field of sign display places expectations on the inkjet recording apparatus capable of forming an image in a simpler and less costly manner than the conventional screen printing or gravure printing.
The textile printing industry uses a fabric of low rigidity as a main recording medium, and the material woven of plastics (polyvinyl chloride), in addition to paper is utilized in the sign display industry. When such a material of low rigidity is used as a recording medium, the recording medium is conveyed generally in close contact with the conveyance belt.
The inkjet recording apparatus where the recording medium is conveyed in close contact with the conveyance belt includes the commonly known inkjet recording apparatus, wherein an adhesive layer using such an upholstering agent as water soluble resin, pressure sensitive resin and heat sensitive resin, and adhesive sheet is formed on the surface of the conveyance belt, and the recording medium is conveyed in close contact with this adhesive layer (See Patent Document 1, for example).
In the inkjet recording apparatus where paper as a recording medium is conveyed by a conveyance belt to record an image, on the other hand, there is a known inkjet recording apparatus. This inkjet recording apparatus has an electrostatic generator arranged on the bottom of the conveyance belt to charge the conveyance belt and to suck a recording medium electrostatically (See Patent Document 2, for example). This inkjet recording apparatus uses an electrostatic generator to charge the conveyance belt electrostatically, and paper is supported by the charged belt, whereby paper is sucked by the conveyor by contact charging.
[Patent Document 1] Official Gazette of Japanese Patent Tokkai 2001-277656
[Patent Document 2] Official Gazette of Japanese Patent Tokkaihei 7-137877
In the inkjet recording apparatus (Patent Document 1) having a conveyance belt provided with a prior art adhesive layer, irregularities are produced on the surface due to repeated adhesion and separation of the recording medium from the conveyance belt; hence, the adhesive strength is reduced by the deposition of dust and contaminants. Thus, the adhesive must be removed for washing at least once in a few months, and adhesive must be applied again. This has taken much time and effort, according to the prior art.
Further, in the aforementioned conventional inkjet recording apparatus, the recording medium is brought in close contact with the conveyance belt by the adhesive layer alone, and the adhesive layer has a high degree of adhesive strength. Once the recording medium is adhered to the conveyance belt, the displacement of the recording medium cannot be corrected, with the result that adhesion and separation are repeated, and much time and effort are required, according to the prior art.
In the inkjet recording apparatus (Patent Document 2) equipped with a conventional electrostatic generator, even when the recording medium impervious to electric charging, including such a fabric such as cotton and silk fabrics or such a woven fabric polyvinyl chloride fabric, is supported by a conveyance belt charged by an electrostatic generator, the recording medium is not sucked by the conveyance belt, so that the recording medium slips on the conveyance belt and accurate conveyance cannot be achieved. This has resulted in production of a defective image, according to this prior art.
The aforementioned prior art inkjet recording apparatus is subject to such a restriction that the conveyance belt is made of the polycarbonate or polyethylene that is susceptible to electrostatic charge.
Further, in the conventional inkjet recording apparatus, the principle of electrostatic suction is based on Coulomb force, and electrostatic suction force is damped by the function of the distance between the conveyance belt and recording medium. Accordingly, the conveyance belt has a thickness of about 0.1 through 0.2 mm. However, if the thickness is small, the durability of the conveyance belt is reduced so that the conveyance belt must be replaced frequently. This has required much time and effort.
To ensure durability of the conveyance belt to a certain extent and to provide accurate transfer of a recording medium, it is possible to consider a method of applying a high voltage to the electrode constituting the electrostatic generator, thereby increasing the electrostatic force. If the applied voltage is increased, however, deflection occurs to ink particles discharged from the recording head to the recording medium, with the result that the position of ink particles hitting the recording medium may deviate.